The Basic lessons · Radio wave propagation · B-007-005

The Sun's Role in Radio Propagation

Learn how the Sun's 11-year cycle and daily radiation change the atmosphere to allow long-distance radio communication. Understand why sunspots and solar flux determine which frequencies work best for reaching distant stations.

This lesson is part of SignalPrep Pro. The subsection's 11 exam questions are free to practise: practise B-007-005.

What this subsection asks

• How do sunspots change the ionization of the atmosphere?
• How long is an average sunspot cycle?
• What is solar flux?
• What is the solar-flux index?
• What influences all radiocommunication beyond ground wave or line-of-sight ranges?
• What effect of the sun's activity influences ionospheric propagation on a daily basis?
• When sunspot numbers are high, how is propagation affected?
• All communication frequencies throughout the spectrum are affected in varying degrees by:
• Average duration of a solar cycle is:
• The ability of the ionosphere to refract high frequency radio signals depends on:
• What is the major cause of cyclical changes in HF propagation?